WeakMap.prototype.has()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The has()
method of WeakMap
instances returns a boolean indicating whether an
element with the specified key exists in this WeakMap
or not.
Try it
Syntax
js
has(key)
Parameters
key
-
The key of the element to test for presence in the
WeakMap
object.
Return value
Returns true
if an element with the specified key exists in the WeakMap
object; otherwise false
. Always returns false
if key
is not an object or a non-registered symbol.
Examples
Using the has method
js
const wm = new WeakMap();
wm.set(window, "foo");
wm.has(window); // returns true
wm.has("baz"); // returns false
Specifications
Specification |
---|
ECMAScript Language Specification # sec-weakmap.prototype.has |
Browser compatibility
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